Gene network is an ensemble of genes expressed in a coordinated mode that controls a vital function of the organism . In this work, we studied the gene network of the cholesterol biosynthesis regulation in the cell and its exchange with the blood plasma cholesterol. A computer model of the dynamics of the gene network function based on a generalized chemical-kinetic simulation method was designed . The model is described in terms of elementary processes (biochemical reactions). The optimal set of values of the parameters used in this model is determined. We performed digital simulation of the dynamic characteristics of the gene network responses to the effects exerted on the system in the normal state and in the case of mutations. The sensitivity of the steady-state content of free cholesterol in the cell to the mutation induced changes occurring in the rates of molecular processes in the gene network was analyzed. We showed that mutations affecting the regulatory processes to the greatest extent influence the steady-state concentration of free cholesterol in the cell.